Temperature indicating paint

ABSTRACT

An irreversible temperature indicating paint comprises 29 wt % to 37 wt % cobalt aluminium spinel and glass, 35 wt % to 45 wt % acrylic resin and 20 wt % to 30 wt % silicone resin excluding solvent. The solvent comprises a mixture of 80% 1-methoxy-2-propanol and 20% dipropylene glycol monomethyl ether. A particular irreversible temperature indicating paint comprises 34.9 wt % cobalt aluminium spinel and glass, 42.5 wt % acrylic resin and 22.6 wt % silicone resin excluding solvent. The irreversible temperature indicating paint has four or more colour changes in the temperature range 500° C. to 900° C. The irreversible temperature indicating paint is used to determine the temperatures to which various parts of turbine blades, turbine vanes or other components are subjected in operation of the gas turbine engine.

[0001] The present invention relates to an irreversible temperatureindicating paint.

[0002] Irreversible temperature indicating paint changes colour at oneor more known temperatures. These colour changes of the temperatureindicating paint indicate the temperature to which different parts of acomponent or components have been subjected. The final colour of theirreversible temperature indicating paint is dependent on both thetemperature it is subjected to and the time period over which it is heldat a raised temperature. The irreversible temperature indicating paintis applied to a component in a test situation and subsequently analysedto determine the temperatures to which different regions of thecomponent reached during the test. Irreversible temperature indicatingpaints thus produce a temperature profile over the whole surface of acomponent rather than discrete points, if for example thermocouples areused.

[0003] Irreversible temperature indicating paints are applied tocomponents, for example turbine blades, turbine vanes and combustors, ofgas turbine engines and the gas turbine engine is run at the gas turbineengines normal operating conditions.

[0004] One known temperature indicating paint described in our UK patentGB1103059 comprises principally lead chromate, magnesium carbonate andsilica.

[0005] Another known temperature indicating paint described in our UKpatent GB2204874 comprises one or more of silver, gold, platinum,palladium, copper, nickel, chromium, titanium and silicon dispersed in10 to 70 wt % solvent and resin.

[0006] Currently used temperature indicating paint used in thetemperature range 500° C. to 900° C. does not provide sufficientresolution of the temperature.

[0007] Accordingly the present invention seeks to provide a novelirreversible temperature indicating paint which has a plurality ofcolour changes in the temperature range 500° C. to 900° C. to provideimproved temperature resolution.

[0008] Accordingly the present invention provides an irreversibletemperature indicating paint comprising cobalt aluminium spinel, glass,a binder and a solvent.

[0009] Preferably the binder comprises acrylic resin and silicone resin.

[0010] Preferably the irreversible temperature indicating paintcomprises 29 wt % to 37 wt % cobalt aluminium spinel and glass, 35 wt %to 45 wt % acrylic resin and 20 to 30 wt % silicone resin excludingsolvent.

[0011] Preferably the irreversible temperature indicating paintcomprises 33 wt % to 37 wt % cobalt aluminium spinel and glass, 37.5 wt% to 45 wt % acrylic resin and 21 to 27.5 wt % silicone resin excludingsolvent.

[0012] Preferably the irreversible temperature indicating paintcomprises 34 wt % to 36 wt % cobalt aluminium spinel and glass, 40 wt %to 45 wt % acrylic resin and 22 to 25 wt % silicone resin excludingsolvent.

[0013] Preferably the irreversible temperature indicating paintcomprises 34.9 wt % cobalt aluminium spinel, 42.5 wt % acrylic resin and22.6 wt % silicone resin excluding solvent.

[0014] Preferably the solvent comprises a mixture of propylene glycolethers. Preferably the solvent comprises a mixture of 80%1-methoxy-2-propanol and 20% dipropylene glycol monomethyl ether.

[0015] The present invention will be more fully described by way ofexample.

[0016] An irreversible temperature indicating paint according to thepresent invention has four or more colour changes in the temperaturerange 500° C. to 900° C. when run at maximum operating conditions of agas turbine engine, or other engine, for 3 minutes.

[0017] The irreversible temperature indicating paint comprises cobaltaluminium spinel, glass, a binder and a solvent.

[0018] The irreversible temperature indicating paint broadly comprises29 wt % to 37 wt % cobalt aluminium spinel and glass, 35 wt % to 45 wt %acrylic resin and 20 wt % to 30 wt % silicone resin excluding solvent.The solvent comprises a mixture of propylene glycol ethers, for examplethe solvent comprises a mixture of 80% 1-methoxy-2-propanol and 20%dipropylene glycol monomethyl ether. The amount of solvent used isvaried depending upon the particular method of applying the irreversibletemperature indicating paint.

[0019] The irreversible temperature indicating paint more narrowlycomprises 33 wt % to 37 wt % cobalt aluminium spinel and glass, 37.5 wt% to 45 wt % acrylic resin and 21 wt % to 27.5 wt % silicone resinexcluding solvent.

[0020] Preferably the irreversible temperature indicating paintcomprises 34 wt % to 36 wt % cobalt aluminium spinel and glass, 40 wt %to 45 wt % acrylic resin and 22 wt % to 25 wt % silicone resin excludingsolvent.

[0021] A particular irreversible temperature indicating paint comprises34.9 wt % cobalt aluminium spinel (CoAl₂O₄) and glass, 42.5 wt % acrylicresin and 22.6 wt % silicone resin excluding solvent. The cobaltaluminium spinel and glass is sold under the trade name 121603Decorating Colour Blue by Degussa Metals Catalysts Cerdec AG ofGeschaftsbereich Cerdec, P.O. Box 110403, D-60039 Frankfurt, Germany.The cobalt aluminium spinel may comprises two or more cobalt aluminiumspinels comprising cobalt and aluminium which have a blue colour or bluegreen colour. Cobalt aluminium spinel comprises cobalt aluminate orcobalt aluminium oxide.

[0022] Decorating Colour Blue 121603 comprises glass and oxides having aCAS-No 65997-17-3, a cobalt aluminium spinel having a CAS-No 1345-16-0and a cobalt aluminium spinel having a CAS-No 68187-11-1.

[0023] The irreversible temperature indicating paint has four or morecolour change points in the temperature range 500° C. to 900° C. Theirreversible temperature indicating paint has improved temperatureresolution in the temperature range 500° C. to 900° C., particularly inthe temperature range 600° C. to 800° C.

[0024] The irreversible temperature indicating paint is applied toturbine blades or turbine vanes or other components of gas turbineengines. The irreversible temperature indicating paint is used todetermine the temperatures to which various parts of the turbine blade,turbine vane or other component are subjected in operation of the gasturbine engine.

[0025] The irreversible temperature indicating paint may be used oncomponents in other engines or other machines or other apparatus todetermine the temperature to which various parts of the component aresubjected in operation.

We Claim:—
 1. An irreversible temperature indicating paint comprisingcobalt aluminium spinel, glass, a binder and a solvent.
 2. Anirreversible temperature indicating paint as claimed in claim 1 whereinthe binder comprises acrylic resin and silicone resin.
 3. Anirreversible temperature indicating paint as claimed in claim 1comprising 29 wt % to 37 wt % cobalt aluminium spinel and glass, 35 wt %to 45 wt % acrylic resin and 20 wt % to 30 wt % silicone resin excludingsolvent.
 4. An irreversible temperature indicating paint as claimed inclaim 3 comprising 33 wt % to 37 wt % cobalt aluminium spinel and glass,37.5 wt % to 45 wt % acrylic resin and 21 wt % to 27.5 wt % siliconeresin excluding solvent.
 5. An irreversible temperature indicating paintas claimed in claim 4 comprising 34 wt % to 36 wt % cobalt aluminium andglass, 40 wt % to 45 wt % acrylic resin and 22 wt % to 25 wt % siliconeresin excluding solvent.
 6. An irreversible temperature indicating paintas claimed in claim 5 comprising 34.9 wt % cobalt aluminium spinel andglass, 42.5 wt % acrylic resin and 22.6 wt % silicone resin excludingsolvent.
 7. An irreversible temperature indicating paint as claimed inclaim 1 wherein the solvent comprises a mixture of propylene glycolethers.
 8. An irreversible temperature indicating paint as claimed inclaim 7 wherein the solvent comprises a mixture of 80%1-methoxy-2-propanol and 20% dipropylene glycol monomethyl ether.